1. Field of the Invention
The present invention relates to a method for the manufacture of a key top for a push button switch preferably used in input devices such as cellular phones and keyboards.
2. Description of Related Art
Switches having a structure consisting of a rubber contact switch and a key top installed on the top portion of the key switch have been generally used as push button switches employed in cellular phones and the like.
Push button switches are also required to have excellent appearance, and the demand for metallic-like switches of this type has recently increased. Technology relating to methods for the manufacture of metallic-like push button switches (referred to as “metallic switches” hereinbelow) of an illumination type, which are used in portable phones, was disclosed in Examined Japanese Patent Application No. 3-23915 and Unexamined Japanese Patent Application 2000-176659. In accordance with this technology, a metal layer is formed on a key top and then part of the metal is evaporated and dissipated with a laser to obtain letters, symbols and the like. Furthermore, when colored, e.g., red or blue, metallic switches rather than switches with metallic colors are manufactured, a transparent colored layer is formed on the key top surface, then a metal layer is formed, and only a metal layer is evaporated with a laser.
However, with the above-described method, because laser processing is employed, mass production is difficult to implement. Furthermore, since the entire procedure, from the first to the last stage, is conducted on the key top, if a defect occurs in the last stage, all the preceding operations become useless and the productivity is poor.
Furthermore, when a colored metallic button is manufactured, though the metal layer is removed with a laser, the transparent colored layer is not removed and remains as is. Thus, in order to remove the metal layer, a short-wavelength laser radiation such as that of YAG (yttrium aluminum garnet) laser has to be used, such short-wavelength laser radiation penetrating through plastics. Therefore, the problem associated with such a method is that the transparent colored layer remains without changes and the color of the light that penetrates through the metallic button is restricted to the color of the colored layer.